Wireless receiver



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Filed April- 26, 1930 INVEIVTOR Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE WIRELESS RECEIVER Application April 26, 1930, Serial No. 447,693 In Great Britain May 1, 1929 6 Claims.

The present invention relates to wireless receivers.

It is an object of the present invention to provide a wireless receiver of relatively simple construction which shall be simple to operate and. which shall be adapted to receive signals over a broad band of wavelengths, for example over the shorter broadcasting band which extends from say 200 to 600 meters and over the longer broadcasting band which extends from say 1000 to 2000 metres.

It is common practice to employ a supersonic heterodyne receiver having ganged tuning controls which are operable from a single knob, and it is usual to vary the frequency of the locally generated oscillations in accordance with the frequency of the waves to be received in such a manner as to produce an intermediate or beat frequency of constant value so that the tuned circuits of the intermediate frequency amplifier may comprise inductances and condensers of fixed values. With such an arrangement, however, it is inconvenient to adapt the receiver for reception over a wide band of Wave-lengths or on two different wave-length bands, such as those above referred to, unless two sets of tuned circuits are provided throughout (excepting in the intermediate frequency amplifier) one set being used for reception on one wave band and the other set for reception on the other wave band. With ganged controls such a receiver is very difilcult to make.

According to the present invention, in a wireless receiver in which a plurality of tuned circuits are controlled by means of a single controlling member, the circuit arrangement is such that the receiver is adapted to operate within one band of wave-lengths as a straight receiver (that is to say the received modulated high frequency oscillations are amplified and detected without the production of an intermediate high frequency) whilst the receiver is adapted to operate within another band of wave-lengths as a supersonic heterodyne receiver. In this way, the same tuned circuits, adjustable by the same ganged controls, may be used for both bands of wave-length.

The invention will be described by way of example with reference to the accompanying drawing which shows the circuit diagram of a radio receiving system embodying the invention.

It will be assumed that the receiver is to work over the band of wave-lengths from 200 to 600 metres, that is, from 1500 to 500 kilocycles, as a straight receiver and over the band from 1000 to 2000 metres, that is, from 300 to kilocycles,

as a supersonic heterodyne receiver.

Referring to the drawing, the system comprises an aerial or antenna circuit I having as potentiometer 2 shunted across its terminals, a local oscillator 3 whose output circuit is coupled with the grid circuit of first detector valve 4, a multistage amplifier 5, 6, I, followed by a second detector 8 whose output is connected to a low frequency amplifier 9, and translating device such as a loudspeaker, ID. The thermionic valves or tubes 5, 6, l of the multi-stage amplifier are coupled by tuned circuits ll, l2, l3 and the neutralization of each stage is efiected by the use of screened grid four-electrode tubes. All the tuned circuits are controlled by the operation of a single knob which is in mechanical connection with a tuning condenser in each of the tuned circuits. The frequency to which the circuits H, 12, I3 can be tuned is made adjustable over the band from 500 to 1500 kilocycles.

When it is desired to receive signals within the higher frequency band, the switches l4, I5, it, which are preferably interlocked soas to be operable by the same member, are operated so as to connect the sliding contact of the potentiometer directly to the input of the multi-stage amplifier, and to effectively disconnect the oscillator 3 and first detector 4 from the remainder of the system. The. receiver is now in a condition for straight reception, the high frequency oscillations received by the aerial circuit being amplified by the valves 5, 6, l and detected by the valve 8 in the usual way. The circuits ll, l2, l3 are, of course, tuned to the frequency of the received signal.

When it is desired to receive signals on the longer wave band, the switches l4, l5, 16 are operated so as to remove the connection between the potentiometer contact and the amplifier input, and to connect the former point to the grid circuit of the first detector 4'. At the same time, the output circuit I! of the first detector is coupled to the input of the amplifier, and the plate of the local oscillator 3 is connected to a point on the high tension source. The receiver is now in a condition for supersonic-heterodyne reception. The oscillations produced in the output circuit I8 of the local oscillator are transferred to the grid circuit of the first detector 4, and the resulting beat oscillation is detected and transferred to the amplifier 5, 6, l, which now acts as the intermediate frequency amplifier. The frequency of the local oscillations is so chosen that the resulting intermediate frequency band covers the same range as the frequency band covered by the tuned circuits H, I2 and 13. Thus, for example, the circuit I 8 may be tuned to produce a local oscillation of a frequency of 600 kilocycles. Employing the sum frequency as the intermediate frequency, this will give over the band of received signals between 150 and 300 kilocycles an intermediate frequency band extending from 750 to 900 kilocycles.

The oscillatory circuits associated with the local oscillator 3 and the first detector 4 are not tunable, the requisite tuning of the receiver being accomplished by means of circuits H, l2 and I3. The receiver is thus tunable over both frequency bands by means of the single control member operating the circuits ll, 12, and I3, and a suitable double scale reading in kilocycles or metres may be provided upon this single control member.

I claim:

1. A signal receiving system including in combination, a fixed tuned first detector, a signal source therefor, a fixed tuned local oscillator coupled therewith to produce intermediate frequency signals by interaction in the first detector, a variably tunable amplifier having a tuning range whereby it is responsive to signals in a band of intermediale frequencies produced by the interaction in the first detector, of received signals in a band of relatively low radio frequencies and oscillations from the local oscillator, and switching means for disconnecting the first detector, removing anode potential from the local oscillator and connecting the amplifier with the signal source, whereby said amplifier may directly be tuned independently of the first detector in the reception and amplification of signals of a different frequency range from said signal source.

2. A signal receiving system according to claim 1 wherein the amplifier includes a plurality of stages the tuning of which is adjusted by a single cont-rolling member.

3. A signal receiving system according to claim 1 in which the frequency of the local oscillator is such that the sum frequency signals, produced through interaction between oscillations therefrom and signals in the band of relatively low radio frequencies, fall within the band over which the amplifier is tunable.

4. In a superheterodyne receiving system, an intermediate frequency amplifier having a plurality of electron tube amplifier circuits simultaneously tunable over a predetermined relatively wide frequency range, electron tube frequency changer means comprising a detector and an oscillator having fixed tuning, a signal source including a circuit having fixed tuning, and switching means for simultaneously connecting said intermediate frequency amplifier with the frequency changer means, connecting the frequency changer means with said circuit and energizing the oscillator of said frequency changer means, and said switching means having an alternative position for de-energizing said oscillaior and connecting said intermediate frequency amplifier with said circuit to the exclusion of the detector.

5. In a superheterodyne receiver, a multi-stage electron tube intermediate frequency amplifier, means for simultaneously tuning a plurality of the said amplifier stages over the same frequency range, a signal receiving circuit connected to said amplifier having a frequency response characteristic such that the amplifier provides the signal selecting means therefor, an electron tube oscillator and detector having fixed tuned circuits for producing intermediate frequency signals within a frequency band included in the tuning range of the intermediate frequency amplifier, and means for simultaneously energizing said oscillator, connecting said detector with said signal receiving circuit and said amplifier with the detector output circuit.

6. In a superheterodyne receiver, the combination of a multi-stage electron tube intermediate frequency amplifier, means for simultaneously tuning a plurality of the amplifier stages over a relatively wide frequency range, frequency changer means including a local electron tube oscillator having fixed tuned frequency determining circuits and having an anode circuit, and means for simultaneously removing anode potential from said circuit and connecting said intermediate frequency amplifier with a signal source other than said frequency changer means.

CHRISTOPHER EDlVI'UND GERVASE BAILEY. 

